The proposed work covers two aspects of the search for the possible proximate carcinogen derived from 7,12-dimethylbenz(a)anthracene (DMBA). Using the microsomes from the breast tissue of the rat as a model system, the formation and metabolism of the K-region epoxide of DMBA are being studied. In addition to the biochemical aspects of the problem, the chemical stability and rate of hydrolysis in aqueous media are being investigated, to assess the limitations of the use of the epoxide in physiological applications. The synthesis of hydroxy derivatives of DMBA are also being carried out by the reaction of dimethyl succinate with methoxy benzoins under Stobbe conditions. These compounds will be tested for their possible metabolic formation from DMBA as well as for their estrogenic and carcinogenic properties.